Efforts to improve upon the various performance properties, including impact resistance, tear resistance and heat sealability among others, as well as the processability of vinyl polymers, including polyalphaolefins (PAOs), are the subject of important research and development. This research has grown especially active with the advent of tactiospecific polypropylenes and other vinyl polymers, using tactioselective catalyst such as metallocene catalysts. Although many of these new, sophisticated plastics have good thermal stability and strength, they tend to be brittle and have inferior impact resistance to other plastic products. Efforts to improve the impact resistance of PAOs have recently centered around polymer blends or post polymerization treatments.
Efforts have also been directed at improving the performance properties and processability of crystalline vinyl polymers such as tactiospecific polyalphaolefins polymers by introducing 1-alkene co-monomers with longer alkyl chains into the molecule as side chains to disrupt the crystal packing efficiency of the crystalline vinyl polymers. Efforts have also been directed at decreasing the tactiospecificity of the resulting vinyl polymer or PAO to find a compromise between strength, heat resistance and impact strength.
Due largely to studies on the polymerization of propene, 1-decene and other vinyl monomers, the mechanism of the polymerization of 1-alkene and the effect of that mechanism on polymer structure is reasonably well understood, providing a strong resource for targeting potentially useful oligomerization methods and oligomer structures.
The present invention takes advantage of the ability to combine a chemical transformation and/or reaction and a product separation using a distillation column reactor (DCR). This technique has been called catalytic distillation. Continuous removal of a desired product from the DCR provide one of the unique features that gives catalytic distillation its technical and economic advantages such as lower energy requirements, higher yields, improved product purity, and lower capital investment.
A DCR is generally a conventional fractionation tower equipped with an overhead condenser, reflux pump, reboiler, and control instrumentation, but additionally equipped or fitted with a reaction zone, containing a catalyst, where reaction and distillation occur simultaneously. Depending upon boiling points, feed components are introduced above or below the catalyst zone or bed. Products, unreacted monomers, and other components are continuously removed from the reaction zone by the distillation process.
Catalytic distillation is suitable only for chemical reactions where the distillation of reaction components occurs in the same temperature and pressure range as the reaction. Thus, operation above the critical point can be a limitation, and the presence of azeotropes or close boiling components may cause difficulties.
The catalyst must be stable and insoluble in the feeds or products. The catalyst should be relatively immune to poisoning because frequent catalyst replacement can be costly. The particular catalyst, which generally is a solid material, can include catalyst coated monoliths, catalyst coated packings, or various types of pocketed catalyst packings.
In operation, the reaction liquid and vapor should be able to freely flow through the catalyst zone without unacceptable pressure hindrance and should be able to come to sufficient contact with catalytically active surface, sites, or regions to ensure that the desired chemical transformation occurs in the reaction zone. Also, the method of catalyst packing should be designed to prevent by-passing. The total bed height, or reaction zone, and its position in the DCR are determined by the feed type and composition, and the products and purity desired.
Generally, the chemical transformation and/or reaction occurs in the liquid phase in the presence of a solid catalyst. However, certain gas phase chemical transformation and/or reaction can also occur at the catalyst surface, especially when the reaction zone temperature is tuned to an intermediate molecular weight product. The desired product, having higher molecular weight and generally a higher boiling point than undesirable, lower molecular weight monomers or products, is then fractionally separated into the bottom portion of the DCR upon leaving the reaction zone.
Catalytic distillation has been used commercially to produce a variety of important chemicals including: methyl tert-butyl ether as described in W. Stadig, Catalytic Distillation, Chemical Processing (February, 1987), U.S. Pat. Nos. 4,232,177 and 4,307,254; cumene by alkylating propylene with benzene as described in J. Shoemaker et al., "Cumene by Catalytic Distillation," Hydrocarbon Processing, p. 57 (June, 1987); synthetic polyalphaolefin (PAO) lubricants using a DCR to keep a volatile catalyst in the DCR to accomplish the oligomerization as described in U.S. Pat. No. 4,907,798; alkylation of aromatic compounds using cationic exchange resin including those containing sulfonic acid groups, naturally occurring zeolites and synthetic zeolites as described in European Pat. Application No. 189,683; and heterogeneous isoparaffin/olefin alkylation and oligomerization of alpha olefins using a composite catalyst comprising a Lewis acid promoted non-zeolite solid inorganic oxide, large pore crystalline molecular sieve and/or ion exchange resins in the presence of water as described in U.S. Pat. No. 4,935,577. Similar, non-DCR processes are described in U.S. Pat. No. 4,384,161, 3,855,342 and 3,862,258.
The catalytic distillation technique has also been used for various chemical separations and transformations including: separating isobutene from a mixture comprising n-butene and isobutene as described in U.S. Pat. Nos. 4,242,530 and 4,215,011 using sulfonic acid modified ion exchange resins; and transetherification as described in U.S. Pat. No. 4,510,336, relates to carried out in a catalytic distillation reactor.
The preceding references are incorporated by reference.
Thus, it would be a substantial advancement in the art to be able to prepare oligomeric products of vinyl monomers with narrow molecular weight distributions for use as polymerizable monomers to improve the performance properties, including impact resistance, and processability of polymers made from the same or different vinyl monomers. Additionally, such oligomers would represent new raw materials for various chemicals heretofor made from alpha olefins, including those with from 6 to 30 carbon atoms.